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LSS Respiratory System > gas transport > Flashcards

gas transport Flashcards

altitude sickness: explain the effects of altitude on oxygen availability, explain the acute and long term compensatory physiological mechanisms to high altitude, explain the pathophysiological cause of high-altitude pulmonary and cerebral oedema, and recall the first line interventions to treat altitude sickness

1
Q

define hypoxia

A

specific environment with low PO2 (conditions)

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2
Q

define hypoxaemia

A

low PaO2 in blood

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3
Q

define ischaemia

A

tissues receiving inadequate oxygen

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4
Q

what can bring on hypoxic stress

A

altitude, exercise, disease (e.g. COPD)

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5
Q

what changes when low PO2 (still 21%) at high altitude and what detects this change

A

low PAO2 (alveolar) and low PaO2 (arterial), activating peripheral chemoreceptors (as opposed to central control using PCO2)

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6
Q

what outflow increased after low PaO2 detected

A

sympathetic nervous system

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7
Q

what 2 responses occur after increased sympathetic nervous system outflow

A

increased ventilation to increase alveolar oxygen and oxygen loading; increase cardiac output and heart rate to increase oxygen loading and tissue delivery

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8
Q

however what does hyperventilation lead to and what is the effect

A

hypocapnia, reducing central drive to breathe, reducing ventilation and hence oxygen loading

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9
Q

what does the CO2 loss cause

A

increased pH (alkalosis), shifting oxygen-dissociation curve left, increasing Hb affinity for O2 and causing decreased O2 unloading

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10
Q

what detects high pH

A

carotid bodies

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11
Q

what is the response to high pH

A

increased HCO3- secretion and causing kidneys to recover and manufacture more H+, normalising oxygen-dissociation curve to increase oxygen unloading

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12
Q

what does low PaO2 also increase

A

erythropoietin production, increasing erythrocyte production and oxygen unloading

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13
Q

why do oxidative enzyme/mitochondrial numbers increase

A

to allow for greater oxygen utilisation to provde energy

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14
Q

why is there a small 2,3-DPG increase

A

shift of oxygen-dissociation curve to right, increasing oxygen unloading

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15
Q

diagram of response to altitude

A

benjis

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16
Q

2 prophylaxis to high altitude

A

acclimation (stimulated by artificial environments e.g. hyperbaric chamber), acetazolamide (carbonic anhydrase inhibitor to accelerate slow renal compensation to hypoxia induced hyperventilation)

17
Q

cause of acute mountain sickness

A

maladaptation to high altitude, with onset within 24 hours of ascent

18
Q

pathophysiology of acute mountain sickness

A

mild cerebral oedema

19
Q

symptoms of acute mountain sickness

A

nausea and vomiting, irritability, dizziness, insomnia, fatigue, dyspnoea

20
Q

consequences of acute mountain sickness

A

HAPE/HACE progression (high altitude pulmonary and cerebral oedemas)

21
Q

treatments of acute mountain sickness

A

stop ascent, analgesia, fluids, hyperbaric O2 therapy

22
Q

cause of chronic mountain sickness

A

idiopathic

23
Q

pathophysiology of chronic mountain sickness

A

secondary polycythaemia increases blood viscosity (higher Hct), so blood sludges through systemic capillaries, impeding O2 delivery

24
Q

symptoms of chronic mountain sickness

A

cyanosis (bluish discolouration), fatigue

25
Q

treatment of chronic mountain sickness

A

remain at low altitude

26
Q

causes of high altitude pulmonary oedema

A

rapid ascent and inability to acclimatise

27
Q

pathophysiology of high altitude pulmonary oedema

A

pulmonary vessel vasoconstriction in response to hypoxia, causing increased pulmonary pressure and permeability which exceeds lymphatic drainage

28
Q

symptoms of high altitude pulmonary oedema

A

dyspnoea, dry cough, bloody sputum, crackling chest sounds

29
Q

consequences of high altitude pulmonary oedema

A

impaired gas exchange

30
Q

treatments for high altitude pulmonary oedema

A

descend, hyperbaric O2 therapy, nifedipine, sildenafil

31
Q

causes of high altitude cerebral oedema

A

rapid ascent and inability to acclimatise

32
Q

pathophysiology of high altitude cerebral oedema

A

cerebral vessel vasodilation in response to hypoxaemia; increased fluid leakage to cranium, compressing brain and raising intra-cranial pressure

33
Q

symptoms of high altitude cerebral oedema

A

confusion, ataxia (poor-coordination), behavioural change, hallucinations, disorientation

34
Q

consequences of high altitude cerebral oedema

A

irrational behaviour, irreversible neurologic damage, coma/death

35
Q

treatments for high altitude cerebral oedema

A

immediate descent, hyperbaric O2 therapy, dexamethasone

LSS Respiratory System (54 decks)

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